1. Field
One or more embodiments of the invention relate to a method and apparatus to couple a device, such as, for example, a capacitor, with a substrate, such as, for example, a printed circuit.
2. Background Information
Capacitors and other devices are may be mounted on printed circuit boards. The capacitors may be physically and electrically coupled with the printed circuit boards through reflow of a solder.
FIG. 1 is an enlarged cross-sectional view showing how a capacitor 120 may be placed on solder bumps 115 that are located on lands 110 of a printed circuit board 105, according to one aspect. Bumps, pads, or other electrical contacts of the capacitor (not shown) may be accurately aligned over the solder bumps and the lands of the printed circuit board.
The solder may be heated until it melts, which may be referred to as reflow. In practice, it may prove difficult to evenly heat all of the solder bumps to the melting point temperature at precisely the same time. Uneven heating of the solder bumps may potentially result in some of the solder bumps melting before others. For example, the right-hand solder bump of FIG. 1 may melt before the left-hand solder bump. The melted solder may exert forces on the capacitor, such as, for example, due at least in part to surface tension. Such forces may be exerted to a lesser extent or not at all by the un-melted solder bump. This may result in an unbalanced force on the capacitor, which may potentially result in the capacitor moving relative to one or more of the lands.
This may potentially result in defects. Commonly encountered defects include, but are not limited to, tombstoning and misalignment of the capacitor.
FIG. 2 is an enlarged cross-sectional view showing how the capacitor may tombstone, according to one aspect. As shown by the arrow, the left-hand end of the capacitor may lift off of the left-hand land.
FIG. 3 is an enlarged top-planar view showing how the capacitor may misalign, according to one aspect. As shown by the arrow, the left-hand end of the capacitor may rotate away from the left-hand land.
Manual correction of tombstoning and misalignment may be possible. However, such manual correction may be time consuming, expensive, and/or may limit production.